Update Contact Manager/Haml

In the section above __Write Less Markup__ instructions were given to add a `to_s` method for the models. The erb file still lists company.name despite refactoring.

Changes: 

- Use to_s method on Company
- Add CSS class "actions" to ul
Add version to haml gem
- Version 3 was the last version of haml to include html2haml
Merge pull request #639 from NanoXD/patch-1

Update Contact Manager/Haml